The overall aim of this proposal if (1) to characterize the Wx locus of Zea mays and quantify its expression at the level of transcription and translation and (2) to determine the molecular basis of the stable mutations of the Wx locus and to analyze how these lesions result in a recessive phenotype. Seven major goals comprise this proposal: (1) isolation of Wx genomic clones from a maize genomic library; (2) characterization of the Wx structural gene as to its DNA sequence, position of Wx mRNA initiation and termination and location of possible introns; (3) quantification of the steady state and transient levels of Wx mRNA during kernel development, correlation of Wx mRNA levels with the synthesis of the Wx preprotein in vitro; (4) generation of physical maps of the Wx locus in wx recessive mutants of spontaneous and induced origin; (5) elucidation f the effect of insertion or deletion mutations on the expression of the Wx locus at the level of transcription; (6) isolation and characterization of genomic DNA containing mutated Wx sequences; (7) genetic analysis of over 25 stable wx alleles to determine if they are, in fact, stable and do not respond to other maize controlling element systems. Characterization of the wild-type Wx locus and its mutant alleles is expected to contribute to a better understanding of the nature of mutation and developmental regulation in a higher plant systems.